Mine doors are frequently used throughout a mine to control ventilation. The doors are typically large and heavy, and they are often opened and closed using hydraulic or pneumatic mechanisms. Examples of such mechanisms are described in U.S. Pat. Nos. 6,425,820, 6,938,372 and 7,118,472. While such mechanisms are generally reliable, they do have certain drawbacks, including complexity and expense. Also, since mine doors are very heavy and subject to large opening and closing pressures due to air flow in the mine, prior mechanisms are designed to move a mine door at slow speeds, which can waste valuable time. Further, the failure of a complex hydraulic or pneumatic mechanism may take substantial time to repair, which can severely impede operations in the mine.
There is a need, therefore, for an improved mine-door opening mechanism.